NZ First MP Brendan Horan is on leave from Parliament after being told by party leader Winston Peters to sort out allegations about money going missing from the bank accounts of his late mother.

Forensic accountants have been asked to investigate his mother's estate, amid allegations that large sums of money were misappropriated from her bank accounts over several years.

Horan has welcomed the investigation, saying he wanted to clear up allegations. He had also said he was considering legal action.

Peters wouldn't say how long Horan had been given. He denied he had been "stood down" .

"You can use any expression you like... His number one priority is to sort this matter out and get the facts before me because that's something on which my future decision is going to be based...it's urgent.

"And I don't mean waiting round for months and months for some legal case."

Peters confirmed he was approached two months ago by Horan's half-brother Mana Ormsby about the allegations.

It was a "long phone conversation and I took some serious notes".

He asked Ormsby to send him more information - which he had not yet received.

"I'd like to see the bank statements, as of now, I have not."

He added: "I have repeatedly asked for the evidence and the facts from the so-called claimant and the executor, and the lawyer for the will. And to date I have received no information at all."

As of yesterday afternoon, no forensic investigation had begun, he said. "That's astonishing."

Peters said he hadn't discussed the matter with Horan in the last 24 hours.

He today twice refused to express confidence in his Tauranga-based list MP.

"Let me tell you, I deal with the facts, and when I see them I'll make my decision then," he said.

"I need the facts on a very serious allegation. And we do take it seriously."

Horan was not at Parliament today. He said he was spending the day in the Bay of Plenty meeting with family members including his sister in Whakatane.

The MP said the matter was a family dispute and he was "disgusted" it had been dragged before the public.

His mother, Olwen Horan, was 87 when she died of cancer in August.

A Mt Maunganui resident, she won about $1 million in prizes, including a house and car, in an Australian lottery in 1999.